Consolidation of bank slippage Mount Sandel Fort (LDY 007:020) Coleraine County Derry

Transcription

1 Monitoring Report No. 282 Consolidation of bank slippage Mount Sandel Fort (LDY 007:020) Coleraine County Derry AE/14/36E Brian Sloan

2 Site Specific Information Site Address: Mount Sandel Fort, Coleraine County Derry Townland: Mount Sandel SMR No.: LDY 007:020 State Care X Scheduled Other Grid Ref: C County: Derry Excavation Licence No: AE/14/36E Planning Ref / No.: N/A Dates of Monitoring: Wednesday 21 st May Friday 6 th June 2014 Archaeologist Present: Brian Sloan Brief Summary: Following sustained wet weather during the winter of 2013/2014, a portion of the bank of Mount Sandel Fort (LDY 007:020) was subject to a landslide along the northern part of its perimeter. To address this slippage and prevent further damage to the monument, a programme of consolidation works was undertaken by the Northern Ireland Environment Agency (NIEA) in association with Whitemountain Ltd. Following the mechanical removal of the slipped material, a series of retaining fences were constructed prior to stone hard-core being used to reform the slipped portion of the bank. A layer of teram was placed over the hard-core with the slipped material being laid on top and grass seed spread. It is hoped that these remedial works will stabilise the bank and act against further slipping occurring in this area of the monument. Nothing of archaeological significance was encountered during the consolidation works, apart from the recovery of lithic artefacts and coarse pottery from an unstratified context. Current Land Use: State Care Monument Intended Land Use: State Care Monument

3 Brief account of the monitoring Introduction Following sustained wet weather during the winter of 2013/2014, a portion of the bank of Mount Sandel Fort (LDY 007:020) was subject to a landslide along the northern part of its perimeter. To address this slippage and prevent further damage to the monument, a programme of consolidation works was undertaken by the Northern Ireland Environment Agency (NIEA) in association with Whitemountain Ltd. All work was carried out under the archaeological supervision of the Centre for Archaeological Fieldwork, Queen s University Belfast (CAF). Following the mechanical removal of the slipped material, a series of retaining fences were constructed prior to stone hard-core being used to re-form the slipped portion of the bank. A layer of teram was placed over the hard-core with the slipped material being laid on top and grass seed spread. It is hoped that these remedial works will stabilise the bank and act against further slipping occurring in this area of the monument. The consolidation work took place over a period of three weeks from 21 st May to the 6 th June Background Mount Sandel Fort (LDY 007:020) is a large oval shaped mound on the eastern bank of the River Bann, approximately 1 mile to the south-west of the town of Coleraine in Co. Derry. The fort rises to a height above the river, and is well protected on the western side by an incredibly steep natural slope. A deep and wide ditch skirts the monument along the eastern side. The environs of the site are renowned for the discovery of an Early Mesolithic settlement site investigated by Professor Peter Woodman in the late 1970s (Woodman 1981). The interpretation of the mound itself is one of debate. Traditionally it has been associated with Dun-de-Beann, a chief stronghold of the Red Branch Knights and well documented in historic sources. However, the association of this monument with Dun-de-Beann is tentative at best, with many scholars now preferring the interpretation of the monument to be a Motte and Bailey (albeit either unfinished or abandoned) dating to the Anglo-Norman excursions into this area in the late 12 th century. Without further excavation within the monument itself, the interpretation can remain but an enigma. Consolidation works Following the slippage it was decided that substantial consolidation work would be necessary to stabilise the monument and prevent further decay. A portion of the bank, varying in width from 10-15m (east/west) had fallen away, exposing the natural reddish-orange natural slope of the original promontory and a thin topsoil layer (maximum thickness of 0.15m) directly lying over. The topsoil consisted of a greyish brown sandy clay with frequent small rounded stones throughout. The mechanical removal of the slipped material was archaeologically supervised and sifted through for any finds (see below). The spoil was set aside on teram for use in the re-instating of the bank. The in situ topsoil, present only at the very top of slope, was left untouched.

4 The finds A small number of unstratified artefacts were recovered from the slippage. On the whole these are flint with undecorated coarse pottery (4 sherds) and modern items (such as golf balls, bottle glass and aluminium tins) also represented. The lithics are dominated by small blades and flakes with at least 3 bladelet cores also included. These date to the Early Mesolithic and are in no doubt associated with the settlement site to the immediate east of the monument. Their presence in this area, albeit from an unstratified context, suggests that the Early Mesolithic activity is not confined to the area investigated by Woodman in the 1970s, but may originally have spread to the promontory on which the fort is situated. This is also borne out by the discovery of Early Mesolithic material in the 1950s to the immediate south of the monument (Collins 1983), as well as when information signage were installed along the forest path to the north-east of the fort (Stef McMullan pers comm.). The pottery sherds have been identified as sherds of Medieval Ulster Coarseware, of probable thirteenth century date (Cormac McSparron pers comm.). This dating could further support the theory that the bulk of the activity at the fort is medieval and perhaps associated with an Anglo-Norman influence in the area. Conclusions The consolidation works at Mount Sandel were successful in that the monument has now been stabilised and further slippage in this area should not occur. The investigation encountered little of archaeological significance save from unstratified lithic artefacts and coarse pottery sherds. As such, no further archaeological mitigation is merited. Publication of the consolidation works is recommended for inclusion in Archaeology Ireland, as well as an inclusion in the annual Excavations Bulletin. References Collins, A., E., P., Excavations at Mount Sandel, Lower Site, Coleraine, County Londonderry. Ulster Journal of Archaeology, Third Series, Vol 46 (1983) 1-22 Woodman, P. C A Mesolithic Camp in Ireland. Scientific American Vol. 245 (1981),

5 Archive: Finds: All finds recovered during the investigation are currently archived at the Centre for Archaeological Fieldwork, Queen s University Belfast Photographs: A total of 154 digital images were generated during the consolidation works. These are currently archived at the Centre for Archaeological Fieldwork, Queen s University Belfast. Plans / Drawings: n/a Signed: Date:

6 Figure 1: Approximate location of Mount Sandel (red dot).

7 2 1 Figure 2: GoogleMap screen grab showing: 1) Approximate location of the slippage; 2) Access to site over Mesolithic habitation area (LDY 007:037)

8 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Figure 3: Approximate location of the slippage area. The proposed access across the paddock to the east of the monument was not used, with the plant accessing the site along the forest path.

9 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Figure 4: Proposed consolidation works.

10 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Plate 1: Slippage prior to the consolidation works, looking south-east. Plate 2: Mechanical removal of the slipped material, looking south-east.

11 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Plate 3: Construction of the upper tier of the retaining fence, looking south.

12 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Undisturbed sod and topsoil Teram Redeposited slipped material Hardcore scree In situ natural slope Retaining fence Plate 4: Detail of the consolidation works, looking west.

13 Centre for Archaeological Fieldwork Monitoring/Evaluation Report No Plate 5: Construction of the second retaining fence, looking south-east. Plate 6: The slipped area following consolidation, looking west. Grass seed was spread on top of the exposed soil to aid in the consolidation of the monument.